This inventions relates to an optical position sensor for apparatus for controlling the winding angle for winding optical filaments onto a bobbin.
More particularly, this invention relates to a countertriangular optical position sensing device for sensing the angle at which optical filament is being wound on the bobbin and for controlling the winding Mechanism and traversing device for maintaining the winding angle at the desired winding angle.
It is known to sense the winding angle at which a filament or yarn is being wound onto a bobbin by using a moveable element or guide through which the yarn or filament passes. Lateral movement of the filament causes the guide to move and the angle in which the filament or yarn is being wound onto the bobbin is sensed, within limits, by the position of the guide element. Such a system has a disadvantage of being inaccurate since the opening in the guide is always larger than the diameter of filament or yarn so that the winding angle may vary without causing the element to indicate the variation. Furthermore, physical contact with the guide or sensing element may tend to damage the filament, especially when delicate fiberoptic glass filaments are concerned.
One process and apparatus for controlling the angle at which the filament is wound onto the bobbin without physical contact with the filament is found in U.S. Pat. No. 4,838,500, issued June 13, 1989 to Gregory S. Graham for "Process and Apparatus for Controlling Winding Angle". This patent discloses a process and apparatus wherein the filament passes through a guide and over an array of light sensing elements arranged in a row, and positioned on centers substantially equivalent to the diameter of the filament. Collimated light is projected onto the array so as to cast a shadow of the filament on one of the light sensing elements in the array. Beams are provided for detecting the particular element on which the shadow of filament falls and for traversing the bobbin at a rate which will maintain the shadow of the filament on the particular light sensing element on which the shadow will fall when the winding angle is at the selected or desired value.
The device in U.S. Pat. No. 4,838,500 is a great improvement over the mechanical devices described above. However, it requires a number of sensors which greatly increases the expense of the apparatus, and the complexity of the multi-cell array, the minimum resolution governed by the size of the array, and the digital output of the array itself are disadvantages. The digital output of the array does not lend itself to use in analog systems.